Preheat the oven to 220 degrees C. Lubricate the baking dish. Thinly chop the potatoes.
Place one layer of potatoes in the bottom of the finished baking dish. Sprinkle potatoes with salt and pepper, 3 tablespoons of flour, 2 tablespoons of oil. Repeat layers until the potatoes run out. Slowly pour milk onto the potatoes.
Bake until the milk boils (check after 15 minutes), and then reduce the power to 190 degrees and bake until the potatoes are soft, from 45 to 60 minutes.